It is in early Beta, but there is a new game for iOS and Android called Sighter. For those familiar with Shutterspot from GPSgames.org, it is very similar, but takes advantage of being a smartphone app.

Launch the app and immediately see tumbnails of interesting nearby sights like statues, gates, signs, doors, street art, etc. You can see the distance and direction, and when you get closer, it turns into an amazing hot-and-cold game. This way you can play hide and seek with interesting sights around you!

If you see something interesting, it's easy to turn it into a Sighter sight for others to discover. Just use the in app camera and let Sighter do its magic.

Of course, it is very new and they are looking for lots of feedback about potential improvements. Also, there will likely not be any near you until you place some and get someone else to try it out.

The developers are geocachers from Hungary and wanted something more city-friendly.